Induction heating



mnuc'rrou HEATING Filed June 30, 1949 1. BECKIUS ET AL June 3, 1952 Patented June 3, 1952 INDUCTION HEATING Ivar Beckius and Hugo Lindstrtim, Vasteras, Sweden, assignors to Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a Swedish corporation Application June 30, 1949, Serial No. 102,368 In Sweden April 20, 1948 4 Claims. 1

This invention relates to a device for local heating of objects to be subjected to soldering, hardening or similar heat treatment by means of high frequency induction currents. Since the low voltage required for. the device generally cannot be produced directly in a generator in a suitable manner, a transformer is needed between the generator and the heating device.

One of the principal objects of the invention is to provide an improved heating device of this kind which allows in a simple manner concentrated heating of the work piece without leakage flux.

Another object is to construct a handy selfcontained device reliable in its function and adapted to be mounted either within a supporting structure or to be used as a manually operated tool.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings and it will be understood that many changes may be made in the details of the construction and arrangement of the parts shown and described without departing from the spirit of the invention expressed in the accompanying claims. The invention, therefore, is not limited to the'exact details of the construction and. arrangement shown and described only by way of example.

Referring to the drawings:

Fig. 1 shows a heating device illustrating diagrammatically the connections of the heating device.

i Fig. 2 shows the heating element of said device viewed from below.

. Fig. 3 shows another embodiment of the heating element also viewed from below.

Fig. 4 shows by way of example partly in section a portable tool containing a heating element according to the principles of the invention.

Like parts throughout the various figures are designated by like reference numerals.

Referring to Fig. 1, the heating device comprises a transformer having a magnetic circuit l, a primary winding 2, and a secondary winding 3. Said secondary winding has a portion 4 which constitutes the eddy current inducing heat producing element for the object to be heated, and which is embedded within a slot 5 in the end surface of a laminated iron core 6 adapted to be brought within the closest vicinity of the work piece to be heated. The slot 5 may be straight but in a preferred shape shown in Fig. 2 it has its ends widened in order to generate a flux concentration in its middle portion with the result that an effective spot heating of the work piece is obtained. Fig. 3 shows a modification, wherein the heating element 4 has the shape of a loop lying in two slots 5 within the end surface of the iron core 6. By this arrangement, a larger area of the Work piece may be heated. Obviously, it is possible to arrange two or more heating elements in corresponding slots.

Fig. 4 shows a portable heating device, use being made of the heating element shown in Figs. 1 2. The transformer has again a magnetic circuit l, supporting a hollow primary winding 2 which is cooled by a cooling fluid. The secondary winding 3 comprises a metal casing l insulatingly surrounding the primary winding 2, two tubular concentric conductors 8 and 9 fixed on the bottom and the top, respectively, of the casing 'l and protruding axially therefrom, and the heating element 4. Said heating element is U-shaped and hollow and has its upwardly extending legs 4a and 41) connected with the outer and the inner tubular conductors 8 and 9, respectively, for instance by soldering. In'order to facilitate the soldering of the leg 4a onto the inner side of the tubular conductor 8, the tube may be cut up in axial direction so that the soldering may be made from the outside. The upper end of the leg to is connected to a tube 10 of insulating material such as rubber for supplying the cooling fluid such as water, whilst the upper end of the leg 4b is connected by a similar tube 1 l with the hollow primary winding 2.

The fluid entering through the tube [0 flows through the conductors 4a, 4, 4b, through the communication tube ll, branches into two sections within the corresponding branches of the primary winding 2, passes these branches and leaves the winding on the primary taps of the transformer through two tubes l2 and [3 which are united to one outlet tube l4.

The iron core 6 in which the heating element 4 is embedded is arranged within the tubular conductor 9. As the iron core is subjected to wear in the long use, it may be provided with means for adjusting its position with respect to the heating element. This may be accomplished by a setting screw I5 by intermediance of an insulating piece 16. As shown in Fig. 4, the depth of the slot 5 is made greater than the height of the conductor 4, and the latter is placed in spaced relationship to the bottom of the slot.

The heating device is provided with a handle ll fixed on the casing 1 and with a switch 18 such as a push button mounted on the handle and connected to feeders l9.

It will be understood that the device described or a plurality thereof also may be used in any desired stationary arrangement, the handle then being replaced by suitable means for attaching the device to thearrangement, such as a machine for soldering, hardening or welding.

We claim as our invention:

1. A high frequency induction heating device for locally heating a work-piece, comprising a transformer primary winding, a transformer-secondary winding consisting of a ringeshapedcasing enclosing the primary winding, an outer tubular conductor extending from ;one-e nd ofsaid casing and an inner tubular conductor extending from the other end of said casing, through the said casing and through the said primary winding and through the outer conductor, a magnetic core contained within and protruding beyond the free ends of said tubular conductors for direct engagement withthe work-:piece, a heating elesmenticonnected tob th said tubular conductors. iatjleastoneslot iormed in the protruding end of said cqreand receivinga portion of said element .-to -.concentrate the heat in the work-piece, said slot .bei-ng suficiently deep-to accommodate the said ,element with the outer surface of the element inwardly spaced from the plane of the work-piece engaging-end of the core, and means .fqr'advancing theisaid core in thesaidinner conductonwhenthe exposed end of the core is Worn down the elementgreceiving slot insaidcore having suflicient depth to permit advancement of the core without moving said element.

2. A high frequency induction heating device according to claim 1, in which the slot in said core .is widenedzat its-tends toconcentrate the magnetic flux within the work-piece.

3. A high frequency induction heating device according to claim 1, in which two parallel slots in close proximity to each other in the end of the core accommodate portions of said element and concentrate the magnetic flux in the work-piece.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1932,4213 Sessions F- Oct. '31, 1933 2,103,716 Frickey Dec. 28, 1937 2,182,820 Pisarev Dec. 12 1939 2,314,865 Bierwirth Mar. 30, 1943 2,509,713 Achard May '30, 1950 

